One of the nice things about my job as a post doc is my working hours: I can work whenever I want and whereever I want (with the small detail that I should come to the office once a day). This flexibility is nice since it allows me to leave early/come in late when I need to and adjust my working schedule to what fits me best. With the small caveat that we sometimes have morning meeetings with mandatory attendance!
However, the flexibility can also be a curse. I can work everywhere, making it very tempting to work when I have a free moment. In recent years I have discovered that my ability to relax is disappearing; instead I am constantly thinking of what work I have to do: writing that new publication we are planning to do, extend my tool with that feature (which would be nice for another publication). I always feel there is something I could be doing instead of sitting on the couch with a book or watching a movie.
This PhD-comics actually captures the situation perfectly.